The present invention is directed to endovascular thin film devices which can be used for treating and preventing stroke, including ischemic stroke caused by a blood clot in a blood vessel in the brain or hemorrhaging stroke caused by aneurysmal subarachnoid hemorrhage.
Cerebrovascular disease is the third leading cause of death in the USA and the leading cause of disability. Strokes affect 500,000 Americans every year. This results in 150,000 stroke-related fatalities per annum, and over 3,000,000 stroke survivors (Wieber et al, Stroke 23:10, 1992). The cost to the community, including health care expenses and lost productivity, has been estimated at over $30 billion per annum. Neurovascular disorders resulting in thrombo-embolic occlusion of intracranial arteries, resulting in ischemic stroke, and rupture of intracranial aneurysms, resulting in hemorrhagic stroke, are major contributors to stroke-related morbidity and mortality world wide. In contrast to cardiovascular disorders, endovascular treatment strategies for neurovascular disorders have been historically limited by issues of safe access to the cerebral vasculature. Over the past decade advances in digital subtraction angiographic techniques and improvements in microcatheter and microguidewire technology have significantly broadened the scope of minimally invasive neuroendovascular therapy. Today, there is an urgent need for developing medical devices specially designed for deployment via catheter-based techniques for percutaneous endovascular treatment of various devastating neurovascular disorders.
Recent clinical data suggest that patients with acute occlusion of intracranial arteries benefit from rapid removal of the intra-arterial clot and experience an improved outcome. Until now, intracranial clot removal has been primarily accomplished by anticoagulation and thrombolysis. There are several disadvantages to this method of clot removal First, the clot composition in many patients makes it not feasible to use urokinase or TPA for thrombolysis. Second, if clot lysis is successful, the problem of reperfusion hemorrhage within the distal vascular bed is dramatically magnified due to the patient""s anticoagulated condition at the time of reperfusion due to prior administration of thrombolytics and heparin. Third, removal of clot by lysis is much more likely to result in distal embolization of small blood clots in a vascular territory that is at the end arteriorlar level and is beyond the help of collateral circulation from adjacent vessels. Due to these shortcomings, an ideal clot removal system would involve mechanical removal of the blood clot from the intracranial vessel without disruption of the patient""s coagulation cascade.
In managing peripheral and coronary atherosclerotic vascular diseases, percutaneous transluminal angioplasty (PTA), usually in combination with percutaneous stent placement, is an alternative to surgical revascularization (Mayberg et al, JAMA, 266:3289-3294, 1991; Moiore et al, Stroke 26:188-201, 1995). There is a growing body of experience with these techniques in the carotid and vertebrobasilar arteries (O""Keefe et al, JACC 16:1097-1102, 1990; Becker et al, Radiology 170:921-940, 1989). Various investigators have stented over 100 arteries with technical success in 95 to 99% of vessels. In addition, the morbidity and mortality rates are comparable to those of CEA (stroke rates of 0-8%, incidence of death 0-0.9%, and restenosis rates of 1-8%). Similar efficacy and safety is observed in angioplasty and stenting of other supra-aortic vessels. Together these data suggest that carotid angioplasty and stenting (CAS) is safe, feasible, and a viable alternative to CEA in the treatment of patients with carotid atherosclerotic disease.
There are two major potential limitations of PTA in managing arterial stenosis: restenosis and distal embolism. Although there is limited long-term follow-up after supra-aortic PTAs, several studies suggest that the restenosis rate is less than 10% at 12 months. This is similar to the results of angioplasty in other vessels where the restenosis rate is related to the size of the vessel and type of lesion. Large vessels such as the iliac and proximal femoral arteries have restenosis rates of 20-25% at three years, while smaller vessels (popliteal and coronary arteries) have restenosis rates of 35-45% (Kachel et al, Neuroradiology 33:191-194, 1991; Criado et al, American Journal of Surgery 174:111-114, 1997). Following CEA restenosis may occur in up to 36% of vessels after a two to ten-year follow up Placing a stent across the vascular segment which has been dilated by PTA reduces the rate of restenosis.
During CEA, transcranial Doppler (TCD) monitoring studies have suggested that emboli may be responsible for half of the cerebrovascular complications of this procedure (Moore et al, Stroke 26:188-201, 1995). A small study has compared TCD of the middle cerebral artery in patients undergoing CEA or PTA (Sundt et al, Mayo Clin. Proc. 50:301-306, 1975). CEA was associated with longer occlusion times and greater reductions in ipsilateral MCA velocity. In contrast thereto, PTA was associated with more micro-embolic signals.
There is an urgent need to develop specially designed medical devices to address the issues of post-angioplasty restenosis and to provide distal protection from thrombo-emboli during PTA. Stents and stent grafts whose size and compliance characteristics are uniquely suited for the carotid vasculature and the vertebro-basilar system both intra- and extracranially are still not commercially available and sorely needed. In addition, distal protection devices that allow continuous distal cerebral perfusion while preventing distal emboli would dramatically improve the safety and feasibility of luminal reconstruction in the cerebral vasculature.
Aneurysmal subarachnoid hemorrhage is a major cause of death and disability in a relatively young patient population. There is an annual incidence of aneurysmal subarachnoid hemorrhage of approximately 10-12 per 100,000 population in most western countries. In the United States nearly 40,000 individuals are hospitalized with aneurysms yearly (Wieber et al, 1992). The natural history of the disease is such that over 30% of patients will die within 24 hours of the bleed, and another 25-30% will succumb in the next four weeks without some form of intervention. As recently as 1993 the only therapeutic option for these patients was surgical management. In the United States, 55-65% of patients suffering aneurysmal subarachnoid hemorrhage do not receive surgical treatment due to their poor medical condition, advanced age, or other factors. This patient population is, instead, relegated to a conservative medical management regimen. The outcome for such non-surgical patients is dismal, with approximately 60% mortality and 25-40% morbidity reported within six months of the original bleed (Weir, Aneurysms Affecting the Nervous System, Chapter II, pp. 19-54, 1987).
Endovascular techniques for the treatment of intracranial aneurysms have been evolving over the past ten or fifteen years. Historically, the endovascular treatment of intracranial aneurysms has been fraught with significant intraoperative morbidity and mortality and poor clinical outcome. Endovascular occlusion has been attempted with a variety of materials from balloons to iron microspheres. The Guglielmi detachable coil, which has been in use in Europe since 1992 and in North America since 1991, provided a major technical advance. Endovascular treatment of intracranial aneurysms has been performed in approximately 4,000 patients worldwide with the Guglielmi detachable coil and has significantly improved the treatment modality by providing a technically safer and more reliable occlusion system.
Data from medical centers with significant endovascular experience suggest complication rates of aneurysm treatment following subarachnoid hemorrhage to be in the range of 1.5-5% mortality and 3-5% morbidity (Byrne et al, J. Neurology, Neurosurgery and Psychiatry, 59(6):616-620, 1995). Post treatment rebleeding rates are less than 1% of treated patients. The treatment modality of the Guglielmi detachable coil involves endovascular microcatheterization of the aneurysm lumen using a coaxial catheter system from a common femoral artery approach. Electrolytically detachable platinum coils are then extruded through the microcatheter and deposited within the aneurysm lumen, thereby filling the aneurysm and excluding the aneurysm lumen from the intracranial circulation and protecting the aneurysm from rupture. This methodology can be effective in the treatment of saccular aneurysms and aneurysms in which the neck to dome ratio is small.
Since its introduction in 1991, the Guglielmi detachable coil has provided a safe, effective, and reproducible endovascular platform for accessing aneurysms throughout the intracranial circulation. However, limitations of the technology have become apparent related to incomplete occlusion of the aneurysm lumen or coil compaction, which results in recanalization of the aneurysm. These limitations are most apparent with particular types of aneurysmal configurations. Wide neck aneurysms or aneurysms that have a small neck but an equally small dome are often not amenable to definitive surgical repair and are difficult or impossible to treat using the Guglielmi detachable coil. In addition, non-saccular intracranial aneurysms, such as fusiform aneurysms and dissecting aneurysms, as well as pseudo aneurysms of intracranial and extracranial vessels, are not adequately treated by surgery or by current endovascular techniques. Examples of this technique can be found in U.S. Pat. Nos. 5,122,136, 5,354,295, and 5,569,680, as well as European Patent No. 750,886.
Stents have historically been used for revascularization to limit abrupt reclosure and restenosis of blood vessels. However, in the case of stents for revascularization, permanent implants have the disadvantage of treating a time-limited disease process, namely post-angioplasty restenosis, which has significant biochemical and cellular mechanisms contributing to its pathogenesis. Slepian (Cardiology Clinics 12(4):715-737, 1994) discloses polymeric endoluminal paving in which biocompatible polymers are applied to the endoluminal surface of an organ and custom-contoured in situ via a catheter to yield a layer or film of polymer in contact with the underlying tissue surface. These tubes or sheets of biodegradable polymers are transported intravascularly via a catheter and positioned at the lesion site and locally remodeled via intraluminal thermoforming of the base line material. Alternatively; fluids are applied to the tissue surface to act as a short-term, thin, chemical interface layer. Another method is to use a polymer film containing interspersed photo-absorbant dye. This method has been used in dissected canine carotid arteries in vitro. However, Slepian recognized that a permanent stent has many disadvantages in preventing restenosis of a blood vessel, and, thus, only biodegradable polymers are used. Slepian used thin tubes or sheets of biodegradable polymers which were transported intravascularly via a catheter and positioned at the lesion site. The polymer is locally remolded via intraluminal thermoforming of the baseline material.
Stereolithography, which is the subject of U.S. Pat. No. 4,575,330, to Hull, is used to form solid shaped objects using computer-generated surface model data to direct an ultraviolet or other laser beam to polymerize a photosensitive mixture of initiators and monomers, such as acrylate monomers. Photopolymerization of multiacrylate monomers up to a thickness of 50 microns has been demonstrated using ultraviolet light radiation in the wave length of 360 nm (Snesen et al, J. Colloid Interface Sci. 179:276-280, 1996). Recently, more powerful and reliable visible lasers, such as Ar+, have been used as the radiation source for the photopolymerization process (Kumar et al, Macromolecules 24:4322, 1991) In addition, mechanical properties of acrylate networks, such as tensile strength, elasticity, and stress response, can be altered by manipulating various photopolymerization parameters (Torres-Filho et al, J. Applied Polymer Science 51:931-937, 1994).
Polymer application to endoluminal surfaces has been pursued for some time in the cardiovascular system. Polymer stents have been investigated as potential alternatives to metal stents in the coronary circulation (van Beusekom et al, Circulation AB6 (supI):I-731, 1992). In addition, chemical processes allowing a polymer to mold and adapt to the underlying tissue topography while generating a smooth balloon molded endoluminal surface have been investigated (Slepian, 1994). Thin hydrogel barriers have been formed on the inner surface of explanted carotid arteries in a rat and rabbit model by in situ photopolymerization in vitro. The illumination conditions in this laboratory model could be varied to control the thickness of the barrier from 10 microns to more than 50 microns (Hill-West et al, Proc. Nat. Acad. Sci. USA 91:5967-5971, 1994).
The last several years have seen significant technological advancement in the application of shape memory alloys in medical devices. Materials with shape memory undergo a phase transformation in their crystal structure under certain specific conditions. This phase transformation, which is inherent within the material, is the basis for the materials unique properties of shape memory and superelasticity. Examples of such applications are found in Kim, U.S. Pat. No. 5,797,920 and Anderson et al, U.S. Pat. No. 5,800,517.
A variety of vascular stents have been proposed. However, none of these has been entirely successful in treating or prevention stroke.
Cowan, in U.S. Pat. No. 5,334,201, describes a permanent vascular reinforcing stent made of a cross-linkable material. A cross-linkable substance is completely encapsulated within a biologically compatible film. Once the stent is in place, a fiber optic means is used to transmit light from a source to a light-emitting tip which is passed inside the catheter to cause the cross-linkable material to cross-link. In this case, the stent is a radially-expansible tubular body portion which is composed of a cross-linkable substance. The stent is not sufficiently pliable to negotiate the tortuous curves of the carotid artery within the skull base. Moreover, the cross-linking technique used by Cowan requires that the balloon be expanded during the entire cross-linking process, thus inhibiting blood flow to the brain. This technique cannot be used in the intracranial circulation, because blood flow to the brain cannot be occluded for a period of time sufficient to cure the polymers used.
Hubbell et al, in U.S. Pat. Nos. 5,410,016 and 5,626,863, disclose photopolymerizable biodegradable hydrogels which can be used to hold vessels or tubes in a particular position for a controlled period of time. Of course, since the hydrogels only remain in the body for a controlled period of time, these hydrogels would not be useful in permanently closing off an aneurysm.
Fearnot et al, in U.S. Pat. No. 5,609,629, disclose an implantable medical device that provides a controlled release of an agent, drug, or bioactive material into the vascular or other system in which a stent or other device is positioned. The polymer can be applied as a coating to a stent, which is preferably composed of a biocompatible material, such as a biocompatible metal.
Buscemi et al, in U.S. Pat. No. 5,443,495, disclose a balloon/stent device for enlarging in situ to fit against a vessel wall, after which the stent is hardened in place. If the material in the stent is activated by light energy, the center shaft of a catheter which introduces the stent to the appropriate location contains an optical fiber.
Choudhury, in U.S. Pat. No. 4,140,126, discloses a method for repairing an aneurysm using a prosthetic graft. The graft comprises an elongated tube which is moveable into a collapsed formation wherein a plurality of folds which extend longitudinally for the length of the tube are interspersed with a plurality of radially-spaced anchoring pins. The tube is preferably collapsed around a carrier line, such as a modified catheter tube, for introduction to the site.
Regan, U.S. Pat. No. 4,795,458, discloses a stent for use after balloon angioplasty made of any nitinol alloy. The stent is in the shape of a helical coil. The stents are treated to make them non-thrombogenic.
Kelly et al, U.S. Pat. No. 5,769,871, disclose an embolectomy catheter for removing an embolus within a vessel, and also review prior devices for removing emboli. Kelly et al do not us a balloon for retrieving material within a blood vessel but use a hollow shaft with a flexible hollow polymeric tip disposed distally off a hingedly flexible annular compartment. The device is pulled through the vessel via a pull on the handle to collect any embolus within.
Dayton, U.S. Pat. No. 5,449,362, discloses a stent which includes a plurality of holes patterned with a desired size, shape, and number to provide a desired bending modulus. This stent is then coated with a polymer or is formed from a polymer which contains a bioactive substance. In this case the holes provide the desired bending.
Winston, in U.S. Pat. No. RE 35,988 and U.S. Pat. No. 5,306,294, discloses a stent in the form of a flexible metal sheet which is closely wound around a spool in a spiral roll. This stent is preferably constructed of a stainless steel foil of about 0.0005 inch thickness. The sheet produces an inherent spring force which expands the sheet from the contracted position in which it is inserted into a vessel.
There are a number of patents which disclose systems for capturing emboli. Daniel et al, U.S. Pat. No. 5,814,064, disclose an emboli-capturing system including an expandable member coupled to a mesh which can be formed in the shape of a cone to capture emboli.
Bourne et al, U.S. Pat. No. 5,649,950, disclose a system for retrieval of a prosthetic occluder. The occluder is formed of a mesh substance and is delivered in a collapsed state.
Ginsburg, U.S. Pat. No. 4,873,978, discloses a vascular catheter including a strainer device at its distal end to capture emboli. The strainer device is in open position when placed in a blood vessel to capture emboli, and in a closed configuration where it is able to retain any captured emboli within its confines.
Kavteladze et al, U.S. Pat. No. 5,683,411, disclose a scent comprising a self-expanding body shaped into the form of a body of revolution, part of which is formed by wire members forming cells of a generally polygonal shape. The body of revolution has a diameter increasing continuously in an axial direction of the body from one end forming an apex towards the opposite end forming a base. This body an be used as an intravenous filter for capture of thrombi or in combination with a blood impermeable membrane as an occlusion device for closing a vessel lumen
The patents to Lefebvre, U.S. Pat. No. 4,990,156; Elsberry, WO 96/3375G; Simon, U.S. Pat. No. 4,425,908; Miller et al, U.S. Pat. No. 5,549,626; Summers et al, U.S. Pat. No. 5,695,519; and Dibie et al, U.S. Pat. No. 5,413,586, all disclose other types of devices for capturing emboli.
Balko et al, U.S. Pat. No. 4,512,338, disclose a stent made of nitinol wire in the shape of a longitudinally oriented coil of adjacent wire loops which is used for restoring patency to an aneurysm. Wiktor, U.S. Pat. No. 4,969,458, discloses a vascular stent made of low memory metal which provides radial support from within a blood vessel. This stent is such that the wire is coiled having a limited number of turns wound in one direction, then reversed and wound in the opposite direction with the same number of turns, then reversed again, etc. This configuration allows for radial expansion of the stent when controlled pressure, such as applied by an inflated balloon, is applied from the inside of the stent.
Mirigian, U.S. Pat. No. 5,578,074; Sharkey et al, U.S. Pat. No. 5,540,701; Neuss, U.S. Pat. No. 5,536,274; Limon, U.S. Pat. No. 5,476,505; Schnepp-Pesch et al, U.S. Pat. No. 5,354,309; Bosley, Jr. et al, U.S. Pat. No. 5,514,176; Froix, U.S. Pat. No. 5,607,467; and Flomenblit et al, U.S. Pat. Nos. 5,876,343, and 5,882,444, all show other types of coiled stents.
Unsworth et al, U.S. Pat. No. 5,846,247, and McNamara et al, U.S. Pat. No. 5,147,370, disclose tubes made from shape memory alloys for use in body tubes.
Cima et al, in U.S. Pat. No. 5,518,680, disclose the use of stereolithography for making tissue regeneration matrices. While the technique can be used for soft tissues, such as blood vessels, there is no indication that this technique can be used in vivo to repair aneurysms.
It would be desirable to develop a medical device platform to improve endovascular treatment options for ischemic and hemorrhagic stroke. Of significant importance is the ability to safely and permanently exclude areas of aneurysmal weakness in the neurovascular circulation, thereby preventing initial or recurrent aneurysmal subarachnoid hemorrhage, as well as ischemic stroke. In addition, low-profile, thin film stents and stent grafts will enable endoluminal reconstruction on the neurovascular circulation and other applications where the internal diameter is small and the route is tortuous. It is also important to be able effectively to retrieve blood clots from the intracranial circulation without altering the body""s coagulation cascade.
It is an object of the present invention to overcome the aforementioned deficiencies in the prior art.
It is another object of the present invention to provide thin film devices for use anywhere in the body, including the vasculature.
It is another object of the present invention to provide methods and apparatus for treating and preventing ischemic and hemorrhagic stroke.
It is another object of the present invention to provide a platform for endovascular treatment for aneurysms in the intracranial circulation.
It is another object of the present invention to provide a method for safely and permanently excluding areas of aneurysmal weakness in the neurovascular circulation, thereby preventing initial or recurrent aneurysmal subarachnoid hemorrhage.
It is still another object of the present invention to provide endovascular thin film devices made of sputtered shape memory alloy thin film.
It is another object of the present invention to provide endovascular thin film devices made of photo-activated monomers encased in a thin biocompatible membrane.
It is a further object of the present invention to provide thin film devices to restore patency to any vessel in the body.
According to the present invention, several types of thin film devices are provided which can be used for treating deficiencies in the vasculature, trachea, esophagus, etc., particularly for treating or preventing ischemic or hemorrhagic stroke:
1. A clot retriever for the acute treatment of ischemic stroke.
2. A platform of devices for intra-cranial stenting for excluding aneurysms and treating atherosclerotic disease. These devices comprise several embodiments broadly referred to as an endoluminal sleeve. The endoluminal sleeve is best suited for treating sidewall aneurysms, fusiform aneurysms, and dissecting aneurysms. The sleeve is located outside of the aneurysmal dilatation within the parent vessel and excludes the aneurysm from the circulation while reconstructing the lumen of the parent vessel. The sleeve can also be used in other areas of the body, e.g., the trachea, colon, and the like.
In one embodiment a conformal sleeve is placed outside the aneurysm to exclude the aneurysm from the circulation. The sleeve is placed in the parent vessel. The sleeve can be optionally fenestrated. The sleeve can be segmented to facilitate its placement around a bend in the vessel. The attachments between segments can be in a linear or a helical configuration. The thin film sleeve in one embodiment can also be bifurcated in order to treat saccular bifurcation aneurysms.
In another embodiment of the endoluminal sleeve the thin film material is in the configuration of a rolled thin film sheet with optional interlocking tabs, and with optional fenestrations. The optional fenestrations can be configured to provide near complete coverage of the vessel, as in a covered stent, or for minimal and selective coverage of the vessel wall, as in an endovascular patch, to cover only the aneurysm neck This design allows for a favorable expansion ratio from a tightly rolled sleeve with multiple overlapping layers for introduction into a blood vessel, to a less rolled configuration with fewer layers of overlap in the deployed state within the blood vessel providing for an endoluminal reconstruction of the blood vessel wall. The sleeve can also be in the form of overlapping rings, which are optionally fenestrated.
3. A platform of endovascular thin film devices for intra-aneurysmal occlusion, provided in several embodiments.
These devices are best suited for treating saccular bifurcation aneurysms, and include a thin film funnel and a thin film hemisphere in the shape of an inverted umbrella. The thin film hemisphere may be made of a single membrane or a series of overlapping membranes.
In another embodiment, the thin film aneurysm occlusion device is in the shape of a sphere or ellipse to be placed within the aneurysm. The proximal half of the sphere, which covers the aneurysm neck, can be a solid membrane in order to occlude the neck of the aneurysm. However, the distal half of the sphere is a largely fenestrated membrane through which a variety of aneurysm occlusion devices can pass, such as polymers, coils, hydrogels, etc. In this manner the coils or hydrogel mass can pass through large fenestrations in the intra-aneurysmal sphere and anchor the thin film intra-aneurysmal device within the aneurysm lumen.
All of the endovascular thin film devices of the present invention are deployed inside the aneurysm, leaving the parent vessel unaffected All of these endovascular thin film devices may be deployed via a hollow delivery guide assembly or a solid delivery guide assembly. In the embodiment covering the hollow delivery guide assembly, the hollow delivery guidewire or guide catheter may have a one-way valve at its distal tip This allows introduction of a volume-filling device, such as a polymer or hydrogel or coils, but would trap these coils of hydrogel or polymer within the aneurysm due to the one-way nature of the valve. All of the aneurysm treatment devices, both the extra-aneurysmal devices, such as the sleeve, or the intra-aneurysmal devices, such as the funnel, hemispheres, or spheres, are detachable devices serving as endoluminal implants. In an additional embodiment, they may also serve as non-implantive devices for aneurysm neck remodeling during endovascular treatment.
4. Also provided are endovascular thin film devices for preventing distal emboli while maintaining antegrate flow within the vessel.
Intracranial Stent Devices
In one embodiment of the present invention, an endoluminal conformal sleeve is provided which is a pliable and collapsible device that is delivered via a microcatheter into the intracranial circulation where it is deployed and undergoes either a shape memory phase transformation or in vivo polymerization to assume the stable configuration of a permanent endoluminal prosthesis. In the inactive state the sleeve remains soft, collapsible, and pliable to ensure its atraumatic delivery through the tortuous curves of the cavernous carotid artery. Upon reaching the endoluminal defect at the site of the aneurysm, the endoluminal conformal sleeve is extruded from the microcatheter. A thin biocompatible membrane with shape memory characteristics is deployed within the vascular lumen where it unfolds to assume a low-profile cylindrical shape of predetermined diameter and length. Alternatively, a thin biocompatible membrane envelope containing a macromolecular precursor is deployed within the vascular lumen where it unfolds to assume a low-profile cylindrical shape of predetermined diameter and length. The soft and pliable sleeve may be segmented to follow the curve of the vessel and conform to its luminal contour. The dimensions are selected so as to provide accurate coverage of the entire base of a saccular aneurysm or the entire length of a fusiform or dissecting aneurysm. Upon deployment, selective angiography can be performed to demonstrate adequate exclusion of the aneurysm from the intracranial circulation. If the position of the endoluminal sleeve is deemed to be inadequate, the collapsible prosthesis can be retracted back into the microcatheter delivery system and removed. After accurate positioning, the conformal sleeve is activated and/or detached.
The endoluminal conformal sleeve of the present invention is formed in situ by constructing the endoluminal conformal device from a material that is able to undergo shape deformation repeatably between two specific predetermined shapes as a function of an applied stimulus. This type of behavior in a material is referred to as dual shape memory effect. Alternatively, the endoluminal conformal sleeve of the present invention can be formed in situ via polymerization of a suitable polymer-forming network or precursor. Polymerization is initiated by suitable polymerization initiators in any combination, such as by heat, light, catalyst, electric field, magnetic field, sonic energy, or any other type of polymerization initiator that can be used to polymerize the precursor in situ.
Intra-Aneurysmal Occlusion Devices
In an other embodiment, the endovascular thin film device is in the form of an endoluminal conformal funnel. The funnel is composed of a collapsible thin film biocompatible membrane with shape memory characteristics which, upon extrusion from a microcatheter, unfolds within the aneurysmal lumen to occlude the aneurysm orifice. The configuration of the funnel is such that its distal diameter is larger than the aneurysm neck and tapers to a smaller proximal orifice with an optional one-way valve through which a packing material may be introduced into the aneurysm fundus in the deployed state. The packing material may include a polymerizing substance, hydrogel, or metallic coil device. These devices can be mechanically deployed within the aneurysm or can be remotely triggered via the introducing guidewire assembly to undergo a phase transformation, thereby filing the aneurysm volume and serving to anchor the funnel at the aneurysm base by exerting radial tension on the funnel membrane, preventing it from migrating from or within the aneurysm.
In another embodiment, the endovascular thin film device may be an umbrella shaped dome or hemisphere composed of a single membrane mounted on a solid introducing guidewire assembly. In yet another embodiment, the endovascular thin film device may be composed of a sphere such that the proximal half of the sphere is a single membrane non-fenestrated dome, while the distal half of the sphere is a richly fenestrated dome. The fenestrations within the distal hemisphere allow the aneurysm volume-filling material to pass freely through the aneurysm occluding sphere and thereby anchor the endovascular thin film device at the aneurysm neck and base by exerting radial tension on the spherical or elliptical endovascular thin film device, holding it in place against the aneurysm dome. The aneurysm volume-filling material may be a shape memory material that is incorporated within the concavity of the dome of the hemispherical device or the spherical or elliptical device. This shape memory material can undergo a triggered phase transformation and expand to fill the aneurysm volume, thereby anchoring the funnel or sphere at the base of the aneurysm by exerting radial tension on the thin film device and preventing it from migrating from or within the aneurysm.
In another embodiment, the endovascular thin film device may be constructed of separate overlapping component membranes which unfold after being extruded from the lumen of the introducing microcatheter and assume the shape of a blossoming flower bud. If a shape memory material that can undergo a triggered phase transformation and expand to fill the aneurysm volume is incorporated within the concavity of the flower bud, analogous to a stamen, the device can be mounted on a solid introducing guidewire assembly. This device undergoes a triggered phase transformation to expand to fill the aneurysm volume, thereby anchoring the funnel at the aneurysm base by exerting radial tension on the funnel membrane, thus preventing it from migrating from or within the aneurysm.
Alternatively, the device may be mounted on a hollow guidewire or guide catheter assembly such that, after deployment of the device, the internal volume of the aneurysm may be accessed through the hollow guidewire and filled with a packing material. Access may be restricted via a one-way valve. This allows filling of the aneurysm volume but contains the volume-filling material within the aneurysm due to the one-way nature of the valve. A variety of packing materials may be used, such as shape memory material, polymerizing material, hydrogel, coils, or other materials or devices, to fill the aneurysm volume and thereby anchor the funnel at the aneurysm base by exerting radial tension on the funnel membrane and preventing it from migrating from or within the aneurysm.
The thin film membranes that compose the device are folded on themselves via stress-induced deformation according to the superelastic properties of the shape memory materials. The device is deployed by extruding it from the catheter, thereby removing the stress and allowing it to revert to its undeformed configuration. Alternatively, the dual shape memory properties of the material may be used and a triggering stimulus provided to induce a phase transformation. After deployment of the device and prior to filing the internal volume of the aneurysm, the device can be retracted into the catheter and removed from the patient if the size and shape characteristics of the device are unsuitable for the local angio-architecture.
In the case in which there is a circumferential endoluminal lining caused by placing the sleeve which may interfere with perfusion of adjacent perforating arteries or vascular branches, the endoluminal sleeve is fenestrated. The fenestrations permit blood flow into the perforating arteries adjacent to the aneurysm lumen.
When the aneurysms are at vessel bifurcations, several modifications of the endoluminal conformal sleeve can be used for treatment. In one embodiment of the present invention, the endoluminal conformal sleeve is made Y-shaped. Alternatively, the endoluminal conformal sleeve can be in the shape of a funnel.
For purposes of the present invention, the term xe2x80x9cendovascular thin film devicexe2x80x9d refers to all of the shape memory or in situ polymerizable devices used to repair aneurysms, irrespective of the shape of the aneurysm or the vessel(s) associated therewith.
In yet another embodiment of the present invention, shape memory or photopolymerizable coils can be used as an intravascular occlusion device.